The invention relates to a pair of scissors, particularly hairdresser's scissors, with a pivot joint comprising a pivot screw and a screw nut, where the pivot screw is connected to one scissor blade in an essentially non-rotating fashion and the screw nut has a flexible body on the circumference of a neck which engages a circular recess in the drilled hole of one scissor blade, or on the face pointing towards the drilled hole, said body contacting the screw nut and the wall of the drilled hole under pressure.
Scissors of this kind are known from German Patent DE-PS 30 23 057. In these scissors, the steel screw nut of the pivot joint has a circular groove around the circumference of its neck, in which a flexible O-ring is inserted. The O-ring contacts the neck of the screw nut and the wall of the drilled hole in the one scissor blade under pressure. Rotation of the screw nut is said to be prevented as a result of the pressure exerted on the neck of the screw nut by the O-ring. In this context, the contact pressure is selected in such a way that the action of the scissors can be sensitively adjusted by turning the screw nut.
The pivot screw in the scissors known from the aforementioned publication has two milled surfaces on opposite sides of its shank, engaging an appropriately shaped aperture in the one scissor blade, the upper blade, in such a way that it is connected to the upper blade of the scissors in an essentially non-rotating fashion.
However, when manufacturing scissors of this kind in bulk, it is impossible to achieve complete freedom from rotation of the connection between pivot screw and upper blade. Consequently, this connection has a certain amount of play which is inherent in the manufacturing process. As the screw nut contacts the upper blade of the scissors in a non-rotating fashion owing to the O-ring on the neck, this play gives rise to play between the screw nut and the pivot screw.
The play between screw nut and pivot screw is particularly disturbing when cutting with precision scissors of the kind mentioned at the start. Modern precision scissors have a closing pressure of approx. 30 g which is set electronically. As a result of the very low closing pressure, the play between the shank of the pivot screw and the aperture in the upper blade or between the screw nut and the pivot screw manifests itself in the form of a jerking effect. These noticeable jerks are unpleasant for the person using the scissors, e.g. the hairdresser. In addition, the jerks increase the wear on the pivot screw. It should be kept in mind in this context that the scissors are operated roughly one thousand times for a normal haircut.